[QGIS-Developer] Access QgsVectorLayer from child algorithm

[Simon Gröchenig]

Yes, that is the method I am looking for. Thank you, Etienne.

I am still curious why the output is different depending on the 
isChildAlgorithm parameter??

Simon


Am 24.11.2021 um 12:50 schrieb Etienne Trimaille:
> This might help you ?
> QgsProcessingUtils::mapLayerFromString()
> https://qgis.org/api/classQgsProcessingUtils.html#aa1c2360e52d2ed8100faf02a35125b17
>
>
> Le mer. 24 nov. 2021 à 11:19, Simon Gröchenig 
> <simon.groechenig at salzburgresearch.at> a écrit :
>
>     Hi developers,
>
>     I am developing a Python processing algorithm with some child
>     algorithms. I am struggling to find a way to access a child
>     algorithm's output vector layer. I want to use
>     isChildAlgorithm=True in order to correctly set the feedback progress.
>
>     * If I use processing.run(...) with setting the parameter
>     isChildAlgorithm to False (= default), the vector layer (via sink)
>     is returned as a QgsVectorLayer.
>     * If I set isChildAlgorithm to True, only the dest_id is returned
>     as a string. I did not find a solution on how I retrieve the
>     corresponding QgsVectorLayer.
>     * Is it intentional that the vector layer is returned as
>     QgsVectorLayer or str (dest_id), depending on the isChildAlgorithm
>     parameter?
>     * How can I access output QgsVectorLayer from a child algorithm?
>
>     This is a minimum example where you can modify the
>     is_child_algorithm parameter:
>
>     parameters = {
>         'INPUT': QgsVectorLayer('Point?crs=epsg:31258', 'locations',
>     "memory"),
>         'DISTANCE': 10,
>         'OUTPUT': 'TEMPORARY_OUTPUT'
>     }
>     result = processing.run("native:buffer", parameters,
>     is_child_algorithm=False )
>     vector_layer = result['OUTPUT']
>     print(str(type(vector_layer)))
>
>     Best regards
>     Simon
>
>     -- 
>     Simon Gröchenig MSc
>     MTA - Mobility & Transport Analytics
>
>     Salzburg Research Forschungsgesellschaft mbH
>     Jakob-Haringer-Straße 5/3 | 5020 Salzburg, Austria
>     T: +43.662.2288-314
>     simon.groechenig at salzburgresearch.at
>     http://www.salzburgresearch.at
>
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-- 
Simon Gröchenig MSc
MTA - Mobility & Transport Analytics

Salzburg Research Forschungsgesellschaft mbH
Jakob-Haringer-Straße 5/3 | 5020 Salzburg, Austria
T: +43.662.2288-314
simon.groechenig at salzburgresearch.at
http://www.salzburgresearch.at
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